The present invention relates to disc drive data storage systems and, more particularly, to a support assembly for precisely locating a disc drive module during servo track writing.
A typical disc drive storage system includes one or more magnetic discs which are mounted for co-rotation on a hub or spindle. A typical disc drive also includes a transducer supported by a hydrodynamic bearing which flies above each magnetic disc. The transducer and the hydrodynamic bearing are collectively referred to as a data head. A drive controller is conventionally used for controlling the disc drive based on commands received from a host system. The drive controller controls the disc drive to retrieve information from the magnetic discs and to store information on the magnetic discs. An electromechanical actuator operates within a negative feedback, closed-loop servo system to move the data head radially or linearly over the disc surface for track seek operations and holds the transducer directly above a desired track or cylinder on the disc surface for track following operations.
Information is typically stored in concentric tracks on the surface of the magnetic discs by providing a write signal to the data head to encode flux reversals on the surface of the magnetic discs representing the data to be stored. In retrieving data from the discs, the drive controller controls the electromechanical actuator so that the data head flies above the desired track or cylinder on the magnetic discs, sensing the flux reversals on the magnetic discs, and generating a read signal based on those flux reversals.
In an embedded servo-type system, servo information or (servo bursts) is recorded on data tracks which also contain stored data. The servo bursts are typically temporally spaced evenly about the circumference of each data track. Data is recorded on the data tracks between the servo bursts. In a dedicated servo-type system, an entire disc surface in a disc drive is dedicated to storing the servo information.
As the data head reads the servo information, the transducer provides a position signal which is decoded by a position demodulator and presented in digital form to a servo control processor. The servo control processor essentially compares actual radial position of the transducer over the disc (as indicated by the embedded servo burst) with a desired position and commands the actuator to move in order to minimize position error.
The servo information is written on the disc surfaces during manufacture of the disc drive module. Each disc drive module is mounted to a servo writer support assembly which precisely locates the disc surfaces relative to a reference or origin. The servo writer support assembly supports a position sensor, such as laser light interferometer, which detects the position of the actuator relative to the disc surfaces. The position sensor is electrically inserted within the disc drive's negative feedback, closed-loop servo system for providing position information to the servo system while the servo data is being written to the disc surfaces. The servo writer support assembly may also support a clock writer transducer which writes a clock pattern onto the disc surface which is used for temporally spacing the servo data about the circumference of each track.
Vibration caused by disc rotation, operation of the spindle motor and actuator movement results in vibration of the disc drive module relative to the servo writer support assembly. The vibration is fed back through the closed-loop servo system as part of the position error signal generated by the actuator position sensor and results in inaccurate servo information being written to the disc surface. Inaccurate servo information limits the ability of the electromechanical actuator to accurately position the data head directly over the desired data track during normal track following operations.
It is therefore desirable for the servo writer support assembly to provide structural and electrical integrity for minimizing the generation of vibrations and the effect of those vibrations on the quality of the servo information that is recorded on the disc surfaces, especially in high aerial density applications. It is also desirable for the servo writer support assembly to provide an interface that supports high volume, automated, manufacturing processes.
The present invention addresses these and other problems, and offers other advantages over the prior art.